Field of the invention
[0001] This invention relates to a photographic dispersion comprising a sucrose derivative
and a photographic compound.
Background of the art
[0002] For the introduction of hydrophobic compounds into hydrophilic photographic layers
is common practice in the photographic industry to disperse a solution in an organic
solvent of the hydrophobic compounds into a water medium, normally in a gelatin and
surfactant water solution. In order to improve stability of such dispersions, the
hydrophobic compounds are frequently dissolved in high boiling organic solvents (also
called in the art permanent solvents, crystalloidal solvents, oil-type solvents, oil-formers
and the like). In some cases, it may be advantageous to facilitate the dissolution
of the hydrophobic compound by using an auxiliary water-immiscible or water-miscible
low boiling organic solvent, which is removed afterwards by evaporation. Permanent
high boiling solvents have a boiling point sufficiently high, generally above 150°C
at atmospheric pressure, such that they are not rapidly evaporated under normal dispersion
making and photographic layer coating procedures. Permanent high-boiling solvents
are primarily used in the conventional "oil-protection" dispersion method whereby
the organic solvent remains in the dispersion, and thereby is incorporated into the
emulsion layer coating solution and ultimately into the photographic element. Typical
permanent solvent are, for example, tricresyl phosphate or dibuthylphtalate.
[0003] Generally a photographic element comprises a plurality of layers, at least one of
which comprises a silver halide emulsion, coated onto a support. During, or just prior
to, the coating step, the dispersion may be heated to about 45°C and maintained at
that temperature for up to 24 hours. It has been noted that in certain cases the dispersed
particles containing the photographically useful compound can undesirably grow in
the dispersion. This particle growth can cause the photographically useful compound
to become less effective for its intended purpose.
[0004] An attempt to slow the particle growth in photographic dispersions is disclosed in
US Patent 4,181,527 to Toda et al. Toda et al. disclose that incorporation of organic
solvent gelling agents, such as N-acylamino acid amides, N-acylamino acid amine salts,
and dehydrated condensates of benzaldehydes and sorbitol or xylitol, into a photographic
dispersion solidifies or "gels" the oil phase of the dispersion, thereby inhibiting
particle growth. While this method does slow particle growth, the resulting viscosity
increase of the dispersed phase containing the photographically useful compound can
result in undesired decreases in performance such as reactivity or lubricity.
[0005] US Patent 5,468,604 discloses that certain hydrophobic, photographically inert compounds
which do not solidify or gel the dispersed liquid organic phase can effectively inhibit
undesired particle growth in photographic dispersions subject to such particle growth.
[0006] US Patent 6,045,985 and EP patent application No. 1,170,629, for example, disclose
photographic dyes showing good solubility into the common permanent solvents; however,
even a good dispersion of these molecules, obtained using tricresyl phosphate or dibuthylphtalate
as permanent solvent, is unstable when stored for a long period of time with an evident
change of the drop size distribution and a consequent increase of the average diameters.
[0007] US Patent 5,451,497 and European Patent Application EP 661,588 describe photographic
dispersions containing photographically useful compounds, a main permanent solvent
and a non-color forming, oil-soluble, monomeric or oligomeric organic compound having
a glass transition temperature between 0° and 150°C, such as, for example, oil-soluble
sucrose esters and rosin and derivatives thereof to inhibit the crystallization of
the photographic useful compounds, in particular of photographic couplers. US Patents
3,564,576; 3,676,142 and 3,516,833 also disclose sucrose esters as auxiliary solvents.
[0008] We have surprisingly found that stable dispersions of a certain class of photographic
compounds, such as for example the compounds described in EP patent application No.
1,170,629, can be easily prepared using a sucrose derivative. The drop size distribution
for the so dispersed photographic compounds is completely inhibited even when stored
for a long period of time (30 days) in a cold room.
Summary of the invention
[0009] The present invention refers to process for preparing a dispersion which comprises
codispersing in an aqueous medium a sucrose derivative represented by general formula
(1):
wherein substituents X
1 to X
8, being the same or different, are represented by a hydrogen atom, an alkyl group
or an acyl group, with the proviso that at least four of the X
1 to X
8 substituents are different from hydrogen and that the total sum of the carbon atoms
of X
1 to X
8 substituents is at least sixteen;
and a photographic compound represented by general formula (2):
wherein
R and
R1 each independently represent a hydrogen atom, a substituted or unsubstituted alkyl
group, a substituted or unsubstituted alkylene group, a substituted or unsubstituted
heterocyclic group or a substituted or unsubstituted aryl group;
R2,
R3 and
R4 each independently represent a hydrogen atom, a substituted or unsubstituted alkyl
group, a substituted or unsubstituted aryl group and R
3 and R
4 may be combined to form a 6-membered ring.
[0010] The present invention also refers to a photographic dispersion comprising a sucrose
derivative represented by previous general formula (1) and a photographic compound
represented by previous general formula (2) dispersed in an aqueous medium and to
a photographic element comprising a film support base having coated on at least one
side thereof at least one hydrophilic colloid emulsion layer comprising said photographic
dispersion.
[0011] The process of the present invention provides photographic dispersions having narrow
drop size distribution even when stored for a long period of time (30 days) in cold
room conditions (5°C).
Detailed description of the invention
[0012] Accordingly, the first aspect of the present invention relates to process for preparing
a dispersion which comprises codispersing in an aqueous medium a sucrose derivative
represented by the above described general formula (1) and a photographic compound
represented by the above described general formula (2).
[0013] In particular, in previous general formula (1), X
1 to X
8 substituents, being the same or different, are represented by a hydrogen atom, a
substituted or unsubstituted alkyl group or a substituted or unsubstituted acyl group.
Preferred alkyl groups include 1 to 8 carbon atom alkyl groups comprising linear or
branched-chain alkyl groups, such as, for example, methyl group, trifluoromethyl group,
ethyl group, propyl group, isopropyl group, butyl group, tert.-butyl group, neo-pentyl
group, and octyl group. Preferred acyl groups include 1 to 8 carbon atom acyls comprising
linear or branched-chain acyls, such as, for example, formyl group, acetyl group,
chloroacetyl group, fluoroacetyl group, trichloroacetyl group, propionyl group, butyryl
group, isobutyryl group, valeryl group, and pivaloyl group, or aromatic acyls, such
as, for example, benzoyl group, phthaloyl group, naphthoyl group, toluoyl group. According
to the substituent type from X
1 to X
8, the sucrose derivatives useful in the present invention are therefore represented
by sucrose ethers or esters. Preferably, the X
1 to X
8 substituents are acyl groups, and more preferably are acyl groups having from 2 to
7 carbon atoms, such as acetyl group, propionyl group, butyryl group, isobutyryl group
or benzoyl group.
[0014] When in the present invention the term "group" is used to define a chemical compound
or substituent, the described chemical material comprises the basic group, ring or
residue and that group, ring or residue with conventional substitutions. When on the
contrary the term "units" is used, only the chemical unsubstituted material is intended
to be included. For instance, the term "alkyl group" comprises not only those alkyl
units such as methyl, ethyl, butyl, octyl, stearyl, etc., but even those units bearing
substituents such as halogen atoms, cyano, oxydryl, nitro, amino, carboxilate groups,
etc. The term "alkyl units" on the contrary comprises only methyl, ethyl, stearyl,
cyclohexyl, etc.
[0015] At least four of the X
1 to X
8 substituents in previous general formula (1) are different from hydrogen; preferably,
at least six of the X
1 to X
8 substituents are different from hydrogen; more preferably, all the X
1 to X
8 substituents are different from hydrogen.
[0016] The total sum of the carbon atoms of X
1 to X
8 substituents in previous general formula (1) is at least sixteen; preferably, at
least twenty; more preferably, at least twenty-four.
[0017] The preferred sucrose derivatives used in the present invention are sucrose benzoate,
sucrose diacetate hexaisobutyrate, sucrose diacetate hexabutyrate, sucrose diacetate
hexapropionate and sucrose triacetate pentaisobutyrate. Sucrose diacetate hexaisobutyrate
is a fully-esterified sucrose molecule, esterified with two acetic acid and six isobutyric
acid moieties, commercially available from Eastman Chemical Co. as SAIB™100. Sucrose
benzoate is a quite fully-esterified sucrose molecule, esterified with at least 7
benzoyl groups, commercially available as Uniplex™ 280 CG. It can be prepared according
to procedures well known in the art of sucrose derivatives. The synthesis has been
described, for example, by Salim N. in Bull. Coll. Sci., 1973, Vol. 14, pages 99-101,
by Fang Yirong in Shanghai Huagong. 1997, Vol. 22, No. 4, pages 10-13 or by Coney,
Charles H. in ACS Symp. Ser., 1977, Vol. 41, Sucrochem., Symp., pages 213-22.
[0018] In formula (2) above, R and R
1 independently represent a hydrogen atom, a substituted or unsubstituted alkyl group,
a substituted or unsubstituted alkylene group, a substituted or unsubstituted heterocyclic
group or a substituted or unsubstituted aryl group. Preferred alkyl groups represented
by R and R
1 include 1 to 8 carbon atom alkyls comprising linear or branched-chain alkyls, such
as methyl, trifluoromethyl, ethyl, propyl, isopropyl, butyl, tert.-butyl and octyl.
Preferred alkylene groups represented by R and R
1 include 1 to 8 carbon atom alkylenes comprising linear or branched-chain alkylenes,
such as ethylene, propylene, isopropylene, butylene, and others. Preferred aryl groups
represented by R and R
1 include 6 to 10 carbon atom aryls, such as phenyl and naphthyl. Preferred heterocyclic
groups represented by R and R
1 include 5 or 6-membered heterocyclic groups which may also be fused with other ring
systems, such as for example furane, thiophene, pyridine, pyrrole and imidazole. These
alkyl, alkylene, heterocycle and aryl groups may be substituted with general substituents
well understood in the chemical arts. Particularly useful substituents include for
instance aryloxy groups (e.g., phenoxy, p-methoxyphenoxy, p-methylphenoxy, naphthyloxy
and tolyloxy); acylamino groups (e.g., acetamide, benzamide, butyramide and tert.-butylcarbonamide);
sulfonamide groups (e.g., methylsulfonamide, benzenesulfonamide and p-tolylsulfonamide);
sulfamoyl groups (e.g., N-methylsulfamoyl, N,N-diethylsulfamoyl and N,N-dimethylsulfamoyl);
carbamoyl groups (e.g., N-methylcarbamoyl and N,N-dimethylcarbamoyl); arylsulfonyl
groups (e.g., tolylsulfonyl); aryloxycarbonyl groups (e.g., phenoxycarbonyl); alkoxy-carbonyl
groups (e.g., alkoxycarbonyl containing from 2 to 10 carbon atoms, such as methoxycarbonyl,
ethoxycarbonyl and benzyloxycarbonyl); alkoxy-sulfonyl groups (e.g., alkoxysulfonyl
containing from 2 to 10 carbon atoms, such as methoxysulfonyl, octyloxysulfonyl and
2-ethylhexylsulfonyl); aryl-oxysul-fonyl groups (e.g., phenoxysulfonyl); alkylureido
groups (e.g., N-methylureido, N,N-dimethylureido and N,N-dibutylureido); arylureido
groups (e.g., phenylureido); halogen atoms, hydroxy, sulfo, sulfate, carboxyl, amino,
alkyl, alkoxy, nitro and cyano groups.
[0019] In formula (2) above R
2, R
3 and R
4 each independently represent a hydrogen atom, a substituted or unsubstituted alkyl
group or a substituted or unsubstituted aryl group (for a detailed description, see
the definitions given for R and R
1) and R
3 and R
4 can combine together to form a 6-membered heterocyclic ring, for instance an indole
ring.
[0020] Among the photographic compounds of formula (2), the particularly preferred ones
are those belonging to the following formula (3):
wherein
R is as defined in formula (2),
X represents a hydrogen atom or a 1 to 6 carbon atom linear or branched-chain alkyl
group, and
Y represents -COO-(CH
2-CH
2-O)
n-Z or -COO-(CH(CH
3)-CH
2-O)
n-Z, where
n=0,1,2 or 3 and
Z being a 1 to 4 carbon atom linear or branched-chain alkyl group.
[0022] The photographic compounds of formula (2) can be prepared according to procedures
well known in the art of organic chemical dyes. The synthesis of photographic compounds
according to formula (2) is described, for example, in EP Patent Application No. 01114950.7.
[0023] In a preferred embodiment, the photographic compound of formula (2) is a filter dye
to be incorporated in a filter layer of any photographic element. Preferably, the
filter dye is a yellow filter dye to be incorporated in a yellow filter layer in any
photographic element where it is desirable to absorb blue light. The yellow filter
layer is especially useful in photographic elements having at least one silver halide
emulsion layer that is sensitive to at least one portion of radiation of the electromagnetic
spectrum other than blue light in addition to its intrinsic sensitivity to blue light.
In such a case, the yellow filter layer can be used to reduce or prevent blue light
from reaching this silver halide emulsion layer, and to assure the response of the
silver halide emulsion to the radiation to which it is sensitized rather than to blue
light.
[0024] One preferred embodiment of the process of the present invention comprises, mixing
the sucrose derivative of formula (1) and the photographic compound of formula (2)
with an aqueous media comprising a surfactant and a hydrophilic colloid, emulsifying
the mixture using any conventional mixing apparatus, and adding the resultant dispersion
into a photographic coating mixture containing a hydrophilic colloid.
[0025] In the process of the present invention, the sucrose derivative of formula (1) and
the photographic compound of formula (2) are preferably mixed together prior to preparing
the dispersion in the aqueous medium. They are preferably mixed in a sucrose derivative
to photographic compound weight ratio of from 0.5:1 to 4:1, more preferably from 1:1
to 3:1.
[0026] Auxiliary water-immiscible or water-miscible low boiling organic solvents well known
in the art, as described, for example, in US patents 2,801,170, 2,801,171 and 2,949,360,
can be preferably added to the mixture of sucrose derivative and photographic compound
used in the present invention. Examples of useful auxiliary organic solvents include
ethyl acetate, carbon tetrachloride, methyl ethyl ketone, benzene, ligroine, methanol,
ethanol, dimethylsulfoxide, tetrahydrofuran, dioxan, and acetone. The auxiliary organic
solvents are preferably added to the mixture of sucrose derivative and photographic
compound used in the present invention in a auxiliary solvent to mixture ratio of
from 0.2:1 to 4:1, more preferably from about 0.5:1 to 2:1.
[0027] Nonionic surfactants can be also preferably added to the mixture of sucrose derivative
and photographic compound used in the present invention. Nonionic surfactants include,
for example, polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether, polyoxyethylene
stearyl ether, polyoxyethylene cetyl ether, polyoxyethylene oleyl ether; polyoxyethylene
alkyl aryl ethers such as polyoxyethylene octyl phenol ether, polyoxyethylene nonyl
phenol ether; polyoxyethylene-polyoxypropylene block copolymers; sorbitan fatty acid
esters such as sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate,
sorbitan monooleate, sorbitan trioleate, sorbitan tristearate; and polyoxyethylene
sorbitan fatty acid esters such as polyoxyethylene sorbitan monolaurate, polyoxyethylene
sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan
trioleate, polyoxyethylene sorbitan tristearate. Preferred nonionic surfactants are
sorbitan fatty acid esters surfactants. Non-ionic surfactants are preferably added
to the mixture of sucrose derivative and photographic compound used in the present
invention in a surfactant to mixture ratio of from 0.02:1 to 0.5:1, more preferably
from about 0.05:1 to 0.2:1.
[0028] The mixture of sucrose derivative and photographic compound is then dispersed in
an aqueous media in order to prepare the resulting photographic dispersion. The aqueous
media preferably comprise a hydrophilic colloid, such as hydrophilic colloids employed
in the emulsion layers as known in the photographic art. Useful hydrophilic colloids
include naturally occurring polymers such as gelatine and gelatine derivatives, and
synthetic organic polymers such as polyvinyl alcohols and their derivatives, acrylamide
polymers, polyvinylacetals, polyacrylates, and additional binders as described in
Research Disclosure, 17643, paragraph IX, December 1978. Useful percentage of gelatine concentration
used in the dispersion of the present invention is in the range of from 1 to 50%,
preferably from 5 to 20%. The aqueous solution to mixture of sucrose derivative and
photographic compound ratio is in the range from 1:1 to 20:1, preferably from 2:1
to 10:1.
[0029] Surfactants are preferably added to the above described aqueous media; specific examples
of a usable surfactant include nonionic, anionic, amphoteric and cationic surfactants.
Nonionic surfactants include the same above described surfactants. Anionic surfactants
contain, for example, acid groups, such as a carboxyl group, a sulfo group, a phospho
group, a sulphuric acid ester group, a phosphoric acid ester group etc., for example,
alkylcarboxylate, alkylsulphonates, alkylbenzenesulphonates, alkylnaphthalenesulphonates,
alkylsulphuric acid esters, alkylphosphoric acid esters, n-acyl-n-alkyltaurines, sulfosuccinic
acid esters, sulphoalkylpolyoxyethylene alkylphenyl ether, polyoxyethylene alkylphosphoric
acid esters etc. Amphoteric surfactants such as amino acids, aminoalkylsulphonic acids,
aminoalkylsulphuric or phosphoric acid esters, alkylbetaines, amine oxides etc.; and
cationic surfactants, such as alkylamines, aliphatic or aromatic quaternary ammonium
salts, heterocyclic quaternary ammonium salts, such as pyridinium salts, imidazolium
salts etc., aliphatic or heterocyclic ring-containing phosphonium or sulfonium salts
etc. may be used. These surfactants are usually added in an amount of no greater than
10 parts by weight per 100 parts by weight of solid contents in the present composition.
Additionally, they can be added individually or in combination of two or more thereof.
[0030] Any conventional apparatus can be used for the preparation of the photographic dispersion
of the present invention, such as, for example, a high-speed mixer or a colloid mill.
The resulting photographic dispersion according to the present invention is then incorporated
into the photographic element of the present invention. The photographic element of
the present invention comprises a film support base having coated on one side thereof
at least one hydrophilic colloid emulsion layer comprising the photographic dispersion
of the present invention.
[0031] In a preferred embodiment, said photographic element relates to a multilayer color
photographic element comprising a support base having deposited thereon, in order
from the support, a red-sensitive silver halide emulsion layer, a green-sensitive
silver halide emulsion layer, and a blue-sensitive silver halide emulsion layer respectively
associated with non-diffusing cyan, magenta and yellow dye-forming couplers.
[0032] When multilayer materials contain multiple red, green and blue sub-layers, these
can be relatively faster and relatively slower sub-layers. These elements additionally
comprise other non-light sensitive layers, such as intermediate layers, filter layers,
antihalation layers and protective layers, thus forming a multilayer structure.
[0033] The photographic dispersion of the present invention can be added to any of the above
described layers. The photographic dispersion of the present invention is preferably
added to filter layers, and, more preferably, is added to yellow filter layer positioned
below the blue sensitive layer and above the green and red sensitive layers.
[0034] The photographic dispersion of the present invention is added to the yellow filter
layer in an amount effective to absorb the blue radiation. Typically, the yellow filter
layer will contain about 0.1 to 1.0, preferably about 0.15 to 0.7, gram of compound
of formula (2) per square meter. The yellow dye will provide an optical density of
0.5 to 3.0, preferably 0.8 to 2.0, density units at its λmax which is typically in
the range of 400 to 470 nm, preferably 410 to 440 nm. However, these amounts, ratios
and optical densities can be varied outside the above ranges depending upon such factors
as the particular photographic element, the yellow filter location in the element,
and the amount of blue radiation which is desired to be absorbed by the yellow filter
layer.
[0035] The silver halides used in the photographic elements of this invention may be a fine
dispersion (emulsion) of silver chloride, silver bromide, silver chloro-bromide, silver
iodo-bromide and silver chloro-iodo-bromide grains in a hydrophilic colloid. Preferred
silver halides are silver iodo-bromide or silver iodo-bromo-chloride containing 1
to 20% mole silver iodide. In silver iodo-bromide emulsions or silver iodo-bromo-chloride,
the iodide can be uniformly distributed among the emulsion grains, or iodide level
can varied among the grains. The silver halides can have a uniform grain size distribution
or a broad grain size distribution. The silver halide grains may be regular grains
having a regular crystal structure such as cubic, octahedral, and tetradecahedral,
or the spherical or irregular crystal structure, or those having crystal defects such
as twin plane, or those having a tabular form, or the combination thereof.
[0036] The term "cubic grains" is intended to include substantially cubic grains, that is
grains which are regular cubic grains bounded by crystallographic faces (100), or
which may have rounded edges and/or vertices or small faces (111), or may even be
nearly spherical when prepared in the presence of soluble iodides or strong ripening
agents, such as ammonia. Particularly good results are obtained with silver halide
grains having average grain sizes in the range from 0.2 to 3 µm, more preferably from
0.4 to 1.5 µm. Preparation of silver halide emulsions comprising cubic silver iodobromide
grains is described, for example, in Research Disclosure, Vol. 184, Item 18431, Vol.
176, Item 17644 and Vol. 308, Item 308119.
[0037] Other silver halide emulsions for use in the photographic elements of this invention
are those which employ one or more light-sensitive tabular grain emulsions. Useful
tabular silver halide grains have an average diameter:thickness ratio (often referred
to in the art as aspect ratio) of at least 2:1, preferably 2:1 to 20:1, more preferably
3:1 to 14:1, and most preferably 3:1 to 8:1. Suitable average diameters of the tabular
silver halide grains range from about 0.3 µm to about 5 µm, preferably 0.5 µm to 3
µm, more preferably 0.8 µm to 1.5 µm. The tabular silver halide grains suitable for
use in this invention have a thickness of less than 0.4 µm, preferably less than 0.3
µm and more preferably less than 0.2 µm.
[0038] The tabular grain characteristics described above can be readily ascertained by procedures
well known to those skilled in the art. The term "diameter" is defined as the diameter
of a circle having an area equal to the projected area of the grain. The term "thickness"
means the distance between two substantially parallel main planes constituting the
tabular silver halide grains. From the measure of diameter and thickness of each grain
the diameter: thickness ratio of each grain can be calculated, and the diameter: thickness
ratios of all tabular grains can be averaged to obtain their average diameter:thickness
ratio. By this definition, the average diameter:thickness ratio is the average of
individual tabular grain diameter:thickness ratios. In practice, it is simpler to
obtain an average diameter and an average thickness of the tabular grains and to calculate
the average diameter:thickness ratio as the ratio of these two averages. Whatever
the used method may be, the average diameter:thickness ratios obtained do not greatly
differ.
[0039] In the silver halide emulsion layer containing tabular silver halide grains, at least
15%, preferably at least 25%, and, more preferably, at least 50% of the silver halide
grains are tabular grains having an average diameter:thickness ratio of not less than
2:1. Each of the above proportions, "15%", "25%" and "50%" means the proportion of
the total projected area of the tabular grains having a diameter:thickness ratio of
at least 2:1 and a thickness lower than 0.4 µm, as compared to the projected area
of all of the silver halide grains in the layer.
[0040] It is known that photosensitive silver halide emulsions can be formed by precipitating
silver halide grains in an aqueous dispersing medium comprising a hydrophilic colloid,
gelatin preferably being used as a hydrophilic colloid.
[0041] The silver halide grains may be precipitated by a variety of conventional techniques.
The silver halide emulsion can be prepared using a single-jet method, a double-jet
method, or a combination of these methods or can be matured using, for instance, an
ammonia method, a neutralization method, an acid method, or can be performed an accelerated
or constant flow rate precipitation, interrupted precipitation, ultrafiltration during
precipitation, etc. References can be found in Trivelli and Smith, The Photographic
Journal, Vol. LXXIX, May 1939, pp. 330-338, T.H. James, The Theory of The Photographic
Process, 4th Edition, Chapter 3, US Patents 2,222,264, 3,650,757, 3,917,485, 3,790,387,
3,716,276, and 3,979,213, Research Disclosure, Dec. 1989, Item 308119 "Photographic
Silver Halide Emulsions, Preparations, Addenda, Processing and Systems", and Research
Disclosure, Sept. 1976, Item 14987.
[0042] One common technique is a batch process commonly referred to as the double-jet precipitation
process by which a silver salt solution in water and a halide salt solution in water
are concurrently added into a reaction vessel containing the dispersing medium.
[0043] In the double jet method, in which alkaline halide solution and silver nitrate solution
are concurrently added in the gelatin solution, the shape and size of the formed silver
halide grains can be controlled by the kind and concentration of the solvent existing
in the gelatin solution and by the addition speed. Double-jet precipitation processes
are described, for example, in GB patents 1,027,146, and 1,302,405, US patents 3,801,326,
4,046,376, 3,790,386, 3,897,935, 4,147,551, and 4,171,224.
[0044] The single jet method in which a silver nitrate solution is added in a halide and
gelatin solution has been long used for manufacturing photographic emulsion. In this
method, because the varying concentration of halides in the solution determines which
silver halide grains are formed, the formed silver halide grains are a mixture of
different kinds of shapes and sizes.
[0045] Precipitation of silver halide grains usually occurs in two distinct stages. In a
first stage, nucleation, formation of fine silver halide grain occurs. This is followed
by a second stage, the growth stage, in which additional silver halide formed as a
reaction product precipitates onto the initially formed silver halide grains, resulting
in a growth of these silver halide grains. Batch double-jet precipitation processes
are typically undertaken under conditions of rapid stirring of reactants in which
the volume within the reaction vessel continuously increases during silver halide
precipitation and soluble salts are formed in addition to the silver halide grains.
[0046] In order to avoid soluble salts in the emulsion layers of a photographic element
from crystallizing out after coating and other photographic or mechanical disadvantages
(stickiness, brittleness, etc.), the soluble salts formed during precipitation have
to be removed.
[0047] In preparing the silver halide emulsions, a wide variety of hydrophilic dispersing
agents for the silver halides can be employed. As hydrophilic dispersing agent, any
hydrophilic polymer conventionally used in photography can be advantageously employed
including gelatin, a gelatin derivative such as acylated gelatin, graft gelatin, etc.,
albumin, gum arabic, agar agar, a cellulose derivative, such as hydroxyethylcellulose,
carboxymethylcellulose, etc., a synthetic resin, such as polyvinyl alcohol, polyvinylpyrrolidone,
polyacrylamide, etc. Other hydrophilic materials useful known in the art are described,
for example, in Research Disclosure, Vol. 308, Item 308119, Section IX.
[0048] The silver halide grain emulsion can be chemically sensitized using sensitizing agents
known in the art. Sulfur containing compounds, gold and noble metal compounds, and
polyoxyalkylene compounds are particularly suitable. In particular, the silver halide
emulsions may be chemically sensitized with a sulfur sensitizer, such as sodium thiosulfate,
allylthiocyanate, allylthiourea, thiosulfinic acid and its sodium salt, sulfonic acid
and its sodium salt, allylthiocarbamide, thiourea, cystine, etc.; an active or inert
selenium sensitizer; a reducing sensitizer such as stannous salt, a polyamine, etc.;
a noble metal sensitizer, such as gold sensitizer, more specifically potassium aurithiocyanate,
potassium chloroaurate, etc.; or a sensitizer of a water soluble salt such as for
instance of ruthenium, rhodium, iridium and the like, more specifically, ammonium
chloropalladate, potassium chloroplatinate and sodium chloropalladite, etc.; each
being employed either alone or in a suitable combination. Other useful examples of
chemical sensitizers are described, for example, in Research Disclosure 17643, Section
III, 1978 and in Research Disclosure 308119, Section III, 1989.
[0049] The silver halide emulsion can be spectrally sensitized with dyes from a variety
of classes, including the polymethyne dye class, which includes the cyanines, merocyanines,
complex cyanines and merocyanines, oxonols, hemioxonols, styryls, merostyryls, and
streptocyanine.
[0050] The cyanine spectral sensitizing dyes include, joined by a methine linkage, two basic
heterocyclic nuclei, such as those derived from quinoline, pyrimidine, isoquinoline,
indole, benzindole, oxazole, thiazole, selenazole, imidazole, benzoxazole, benzothiazole,
benzoselenazole, benzoimidazole, naphthoxazole, naphthothiazole, naphthoselenazole,
tellurazole, oxatellurazole.
[0051] The merocyanine spectral sensitizing dyes include, joined by a methine linkage, a
basic heterocyclic nucleus of the cyanine-dye type and an acidic nucleus, which can
be derived from barbituric acid, 2-thiobarbituric acid, rhodanine, hydantoin, 2-thiohydantoin,
2-pyrazolin-5-one, 2-isoxazolin-5-one, indan-1,3-dione, cyclohexane-1,3-dione, 1,3-dioxane-4,6-dione,
pyrazolin-3,5-dione, pentane-2,4-dione, alkylsulfonylacetonitrile, malononitrile,
isoquinolin-4-one, chromane-2,4-dione, and the like.
[0052] One or more spectral sensitizing dyes may be used. Dyes with sensitizing maxima at
wavelengths throughout the visible and infrared spectrum and with a great variety
of spectral sensitivity curve shapes are known. The choice and relative proportion
of dyes depends on the region of the spectrum to which sensitivity is desired and
on the shape of the spectral sensitivity desired.
[0053] Examples of sensitizing dyes can be found in Venkataraman,
The Chemistry of Synthetic Dyes, Academic Press, New York, 1971, Chapter V, James,
The Theory of the Photographic Process, 4th Ed., Macmillan, !977, Chapter 8, F.M.Hamer,
Cyanine Dyes and Related Compounds, John Wiley and Sons, 1964, and in Research Disclosure 308119, Section III, 1989.
[0054] The silver halide emulsions can contain optical brighteners, antifogging agents and
stabilizers, filtering and antihalo dyes, hardeners, coating aids, plasticizers and
lubricants and other auxiliary substances, as for instance described in Research Disclosure
17643, Sections V, VI, VIII, X, XI and XII, 1978, and in Research Disclosure 308119,
Sections V, VI, VIII, X, XI, and XII, 1989.
[0055] The silver halide emulsion can be used for the manufacture of multilayer light-sensitive
silver halide color photographic elements, such as color negative photographic elements,
color reversal photographic elements, color positive photographic elements, false
color address photographic elements (such as those disclosed in US patent 4,619,892)
and the like, the preferred ones being color negative photographic elements.
[0056] Suitable color couplers are preferably selected from the couplers having diffusion
preventing groups, such as groups having a hydrophobic organic residue of about 8
to 32 carbon atoms, introduced into the coupler molecule in a non-splitting-off position.
Such a residue is called a "ballast group". The ballast group is bonded to the coupler
nucleus directly or through an imino, ether, carbonamido, sulfonamido, ureido, ester,
imido, carbamoyl, sulfamoyl bond, etc. Examples of suitable ballasting groups are
described in US patent 3,892,572.
[0057] The non-diffusible couplers are introduced into the light-sensitive silver halide
emulsion layers or into non-light-sensitive layers adjacent thereto. On exposure and
color development, said couplers give a color which is complementary to the light
color to which the silver halide emulsion layers are sensitive. Consequently, at least
one non-diffusible cyan-image forming color coupler, generally a phenol or an α-naphthol
compound, is associated with red-sensitive silver halide emulsion layers, at least
one non-diffusible magenta image-forming color coupler, generally a 5-pyrazolone or
a pyrazolotriazole compound, is associated with green-sensitive silver halide emulsion
layers and at least one non-diffusible yellow image forming color coupler, generally
an acylacetanilide compound, is associated with blue-sensitive silver halide emulsion
layers.
[0058] The color couplers may be 4-equivalent or 2-equivalent couplers, the latter requiring
a smaller amount of silver halide for color production. As it is well known, 2-equivalent
couplers derive from 4-equivalent couplers since, in the coupling position, they contain
a substituent which is released during coupling reaction. 2-equivalent couplers which
may be used in silver halide color photographic elements include both those substantially
colorless and those which are colored ("masking couplers"). The 2-equivalent couplers
also include white couplers which do not form any dye on reaction with the color developer
oxidation products. The 2-equivalent color couplers include also DIR couplers which
are capable of releasing a diffusing development inhibiting compound on reaction with
the color developer oxidation products.
[0059] The most useful cyan-forming couplers are conventional phenol compounds and α-naphthol
compounds. Examples of cyan couplers can be selected from those described in US patents
2,369,929; 2,474,293; 3,591,383; 2,895,826; 3,458,315; 3,311,476; 3,419,390; 3,476,563
and 3,253,924; in GB patent 1,201,110, and in Research Disclosure 308119, Section
VII, 1989.
[0060] The most useful magenta-forming couplers are conventional pyrazolone type compounds,
indazolone type compounds, cyanoacetyl compounds, pyrazoletriazole type compounds,
etc. and particularly preferred couplers are pyrazolone type compounds. Magenta-forming
couplers are described for example in US patents 2.600.788, 2.983.608, 3.062.653,
3.127.269, 3.311.476, 3.419.391, 3.519.429, 3.558.319, 3.582.322, 3.615.506, 3.834.908
and 3.891.445; in DE patent 1.810.464, in DE patent applications 2.408.665, 2.417.945,
2,418.959 and 2.424.467; in Japanese Patent applications 20826/76, 58922/77, 129538/74,
74027/74, 159336/75, 42121/77, 60233/75, 26541/76 and 55122/78.
[0061] The most useful yellow-forming couplers are conventional open-chain ketomethylene
type couplers. Particular examples of such couplers are benzoyl acetanilide type and
pivaloyl acetanilide type compounds. Yellow-forming couplers that can be used are
specifically described in US patents 2,875,057, 3,235,924, 3,265,506, 3,278,658, 3,369,859,
3,408,194, 3,415,652 3,528,322, 3,551,151, 3,682,322, 3,725,072 and 3,891,445, in
DE 2,219,917, 2,261,361 and 2,414,006, GB 1,425,020, JP 10,783/76, 26,133/72, 73,147/73,
102,636/76, 6,341/75, 123,342/75, 130,442/75, 1,827/76, 87,650/75, 82,424/77 and 115,219/77,
and in Research Disclosure 308119, Section VII, 1989.
[0062] Colored couplers can be used which include those described for example in US patents
3,476,560, 2,521,908 and 3,034,892, in JP 2,016/69, 22,335/63, 11,304/67, 32,461/69,
26,034/76 and 42,121/77 and in DE 2,418,959. The light-sensitive silver halide color
photographic element may contain high molecular weight color couplers as described
for example in US patents 4,080,211, EP 27,284 and DE 1,297,417, 2,407,569, 3,148,125,
3,217,200, 3,320,079, 3,324,932, 3,331,743, and 3,340,376, and in Research Disclosure
308119, Section VII, 1989.
[0063] Colored cyan couplers can be selected from those described in US patents 3,934,802;
3,386,301 and 2,434,272, colored magenta couplers can be selected from the colored
magenta couplers described in US patents 2,434,272; 3,476,564 and 3,476,560 and GB
1,464,361. Colorless couplers can be selected from those described in GB patents 861,138;
914,145 and 1,109,963 and US 3,580,722 and in Research Disclosure 308119, Section
VII, 1989.
[0064] Also, couplers providing diffusible colored dyes can be used together with the above
mentioned couplers for improving graininess and specific examples of these couplers
are magenta couplers described in US patent 4,366,237 and GB 2,125,570 and yellow,
magenta and cyan couplers described in EP patent 96,873, DE 3,324,533 and in Research
Disclosure 308119, Section VII, 1989.
[0065] Also, among the 2-equivalent couplers are those couplers which carry in the coupling
position a group which is released in the color development reaction to give a certain
photographic activity, e.g. as development inhibitor or accelerator, either directly
or after removal of one or further groups from the group originally released. Examples
of such 2-equivalent couplers include the known DIR couplers as well as DAR and FAR
couplers. Typical examples of said couplers are described in DE patents 2,703,145,
2,855,697, 3,105,026, 3,319,428, 1,800,420, 2,015,867, 2,414,006, 2,842,063, 3,427,235,
3,209,110, and 1,547,640, GB 953,454 and 1,591,641, EP 89,843, 117,511, 118,087, and
301,477 and in Research Disclosure 308119, Section VII, 1989.
[0066] Examples of non-color forming DIR coupling compounds which can be used in silver
halide color elements include those described in US patents 3,938,996; 3,632,345;
3,639,417; 3,297,445 and 3,928,041; DE 2,405,442; 2,523,705; 2,460,202; 2,529,350
and 2,448,063; JP 143,538/75 and 147,716/75, GB 1,423,588 and 1,542,705 and 301,477
and in Research Disclosure 308119, Section VII, 1989.
[0067] In order to introduce the couplers into the silver halide emulsion layer, some conventional
methods known to the skilled in the art can be employed. According to US patents 2,322,027,
2,801,170, 2,801,171 and 2,991,177, the couplers can be incorporated into the silver
halide emulsion layer by the dispersion technique, which consists of dissolving the
coupler in a water-immiscible high-boiling organic solvent and then dispersing such
a solution in a hydrophilic colloid under the form of very small droplets. The preferred
hydrophilic colloid is gelatin, even if some other kinds of colloids can be used.
[0068] Another type of introduction of the couplers into the silver halide emulsion layer
consists of the so-called "loaded-latex technique". A detailed description of such
technique can be found in BE patents 853,512 and 869,816, US 4,214,047 and 4,199,363
and EP 14,921. It consists of mixing a solution of the couplers in a water--miscible
organic solvent with a polymeric latex consisting of water as a continuous phase and
of polymeric particles having a mean diameter ranging from 0.02 to 0.2 µm as a dispersed
phase.
[0069] Another useful method is further the Fisher process. According to such a process,
couplers having a water-soluble group, such as a carboxyl group, a hydroxy group,
a sulfonic group or a sulfonamido group, can be added to the photographic layer for
example by dissolving them in an alkaline water solution.
[0070] Useful methods of introduction of couplers into silver halide emulsions are described
in Research Disclosure 308119, Section VII, 1989.
[0071] The layers of the photographic element can be coated on a variety of supports, such
as cellulose ester supports (e.g., cellulose triacetate supports), paper supports,
polyester film supports (e.g., polyethylene terephthalate or PET film supports and
polyethylene naphthalate or PEN film supports), and the like, as described in Research
Disclosure 308119, Section XVII, 1989. Preferred supports are the polyester film supports,
well known in the art and that can be prepared from any of the polyester compositions
described, for example, in US Patents 2,943,937 or 2,627,088. Suitable polyesters
for use as supports include those prepared from dicarboxylic acids or derivatives
thereof, such as terephthalic acid, isophthalic acid, 2,6-naphthalene dicarboxylic
acid, 2,7-naphthalene dicarboxylic acid, adipic acid, succinic acid and mixtures thereof
and glycols, such as, ethylene glycole, propylene glycole, bytylene glycole, hexamethylene
glycole, cyclohexane diol and mixtures thereof. Especially useful polyester film supports
are polytethylene terephthalate (PET) or polyethylene naphthalate (PEN).
[0072] The supports preferably are initially treated with a surface activation treatment
such as, for example, a corona discharge treatment, a glow discharge treatment, an
active plasma treatment, a chemical treatment, a mechanical treatment, a UV treatment,
flame and similar. The preferred methods are corona discharge treatment, as described,
for example, in US Patents 4,055,685; 4,135,932; 4,220,471 and 5,194,291; and glow
discharge treatment as described, for example, in US Patents 3,288,638; 4,451,497;
4,933,267 and 5,425,980. The photographic elements according to this invention can
be processed after exposure to form a visible image. During processing, the photographic
compound of formula (2) will be generally bleached and/or discharged. Typically, after
processing, the yellow filter layer will contribute less than 0.05, preferably less
than 0.02, density unit to the minimum density areas of the exposed and processed
element. Processing can be the common processing employed to develop color photographic
elements. A negative colored image can be obtained by color development followed by
bleaching and fixing. Development is obtained by contacting the exposed silver halides
of the element with an alkaline aqueous medium in the presence of an aromatic primary
amine color developing agent contained in the medium or in the material, as known
in the art. The aromatic primary amine color developing agent used in the photographic
color developing composition can be any of known compounds of the class of p-phenylendiamine
derivatives, widely employed in various color photographic process. Particularly useful
color developing agents are the p-phenylenediamine derivatives, especially the N,N-dialkyl-p-phenylenediamine
derivatives wherein the alkyl groups or the aromatic nucleus can be substituted or
not substituted.
[0073] Examples of p-phenylenediamine developers include the salts of: N,N-diethyl-p-phenylenediamine,
2-amino-5-diethylamino-toluene, 4-amino-N-ethyl-N-(α-methanesulfonamidoethyl)-m-toluidine,
4-amino-3-methyl-N-ethyl-N-(α-hydroxyethyl)-aniline, 4-amino-3-(α-methylsulfonamidoethyl)-N,N-diethylaniline,
4-amino-N,N-diethyl-3-(N'-methyl-α-methylsulfonamido)-aniline, N-ethyl-N-methoxy-ethyl-3-methyl-p-phenylenediamine
and the like, as described, for instance, in US patents 2,552,241; 2,556,271; 3,656,950
and 3,658,525.
[0074] Examples of commonly used developing agents of the p-phenylene diamine salt type
are: 2-amino-5-diethylaminotoluene hydrochloride (generally known as CD2 and used
in the developing solutions for color positive photographic material), 4-amino-N-ethyl-N-(α-methanesulfonamidoethyl)-m-toluidine
sesquisulfate monohydrate (generally known as CD3 and used in the developing solution
for photographic papers and color reversal materials) and 4-amino-3-methyl-N-ethyl-N-(β-hydroxy-ethyl)-aniline
sulfate (generally known as CD4 and used in the developing solutions for color negative
photographic materials).
[0075] The color developing agents are generally used in a quantity from about 0.001 to
about 0.1 moles per liter, preferably from about 0.0045 to about 0.04 moles per liter
of photographic color developing compositions.
[0076] In the case of color photographic materials, the processing comprises at least a
color developing bath and, optionally, a prehardening bath, a neutralizing bath, a
first (black and white) developing bath, etc. These baths are well known in the art
and are described for instance in Research Disclosure 17643, 1978, and in Research
Disclosure 308119, Sections XIX and XX, 1989.
[0077] After color development, the image-wise developed metallic silver and the remaining
silver salts generally must be removed from the photographic element. This is performed
in separate bleaching and fixing baths or in a single bath, called blix, which bleaches
and fixes the image in a single step. The bleaching bath is a water solution having
a pH equal to 5.60 and containing an oxidizing agent, normally a complex salt of an
alkali metal or of ammonium and of trivalent iron with an organic acid, e.g., EDTA.Fe.NH4,
wherein EDTA is the ethylenediamino-tetracetic acid, or PDTA.Fe.NH4, wherein PDTA
is the propylenediaminotetraacetic acid. While processing, this bath is continuously
aired to oxidize the divalent iron which forms while bleaching the silver image and
regenerated, as known in the art, to maintain the bleach effectiveness. The bad working
of these operations may cause the drawback of the loss of cyan density of the dyes.
[0078] Further to the above mentioned oxidizing agents, the blix bath can contain known
fixing agents, such as for example ammonium or alkali metal thiosulfates. Both bleaching
and fixing baths can contain other additives, e.g., polyalkyleneoxide compounds, as
described for example in GB patent 933,008 in order to increase the effectiveness
of the bath, or thioether compounds known as bleach accelerators.
[0079] The present invention will be illustrated with reference to the following examples,
but it should be understood that these examples do not limit the present invention.
Example
[0080] Sample 1 (comparison). 4g of the photographic compound (I-1) used in the present
invention were dissolved in a mixture of 8g of tricresylphosphate (TCP) and 8g of
ethyl acetate as auxiliary solvent. The mixture was added to 60g of an aqueous 10%
by weight gelatin solution and 6g of an aqueous 10% by weight Hostapur™SAS (a trade
mark of Hoechst AG, West Germany, for an alkane sulfonate) solution as an anionic
surfactant using a Polytron™PT 6045/6 equipment. Water was added to make 100 grams
of final dispersion.
[0081] Sample 2 (comparison) was prepared as Sample 1, but the TCP has been replaced by
dibuthylphthalate (DBP), in the same amount.
[0082] Sample 3 (invention) was prepared as Sample 1, but the TCP has been replaced by sucrose
diacetate hexaisobutyrate (commercially available from Eastman Chemical Co. as SAIB™100),
in the same amount.
[0083] Sample 4 (invention) was prepared as Sample 3, with the addition in the oil phase
of 1g of sorbitan monolaurate (commercially available from Atlas/ICI as Span™20).
[0084] Sample 5 (invention) was prepared as Sample 4, with the addition in the oil phase
of 2g of sorbitan monolaurate.
[0085] Sample 6 (invention) was prepared as Sample 1, but the TCP has been replaced by sucrose
benzoate (commercially available from Uniplex Chemical Co. as Uniplex™ 280 CG), in
the same amount.
[0086] The final composition of the dispersions is reported below in Tab. 1 expressed in
grams per 100 grams of final dispersion:
Table 1
|
Sample 1 (comp.) |
Sample 2 (comp.) |
Sample 3 (invent.) |
Sample 4 (invent.) |
Sample 5 (invent.) |
Sample 6 (invent.) |
Photographic compound (I-1) |
4 |
4 |
4 |
4 |
4 |
4 |
TCP |
8 |
|
|
|
|
|
DBP |
|
8 |
|
|
|
|
SAIB 100 |
|
|
8 |
8 |
8 |
|
Sucrose benzoate |
|
|
|
|
|
8 |
Ethyl acetate |
8 |
8 |
8 |
8 |
8 |
8 |
Span20 |
|
|
|
1 |
2 |
|
Gelatine 10% |
60 |
60 |
60 |
60 |
60 |
60 |
Hostapur™ SAS 10% |
6 |
6 |
6 |
6 |
6 |
6 |
Water to make 1 liter |
|
|
|
|
|
|
[0087] The cold room shelf life (about 5°C) of the Samples 1-6 was monitored through drop
size distribution measurements carried out with a Malvern Mastersizer™ (Light Laser
Scattering) equipment, measured in µm. The results are reported in Tab.2.
Table 2
|
Sample 1 (comp.) |
Sample 2 (comp.) |
Sample 3 (invent.) |
Sample 4 (invent.) |
Sample 5 (invent.) |
Sample 6 (invent.) |
Fresh |
0.38 |
0.38 |
0.32 |
0.26 |
0.26 |
0.22 |
3 days 5°C |
0.41 |
0.45 |
0.36 |
0.32 |
0.26 |
0.22 |
7 days 5°C |
0.45 |
0.43 |
0.39 |
0.32 |
0.26 |
0.22 |
15 days 5°C |
0.53 |
0.53 |
0.43 |
0.38 |
0.32 |
0.22 |
30 days 5°C |
0.75 |
0.67 |
0.45 |
0.38 |
0.33 |
0.22 |
[0088] Table 2 shows that the distribution size of comparison Samples 1 and 2, obtained
by a dispersion process comprising TCP and DBP as permanent solvent, greatly increase
during long storage. On the contrary, Samples 3-6 obtained by a dispersion process
according to the present invention show a little variation of said values.